Most lawn and garden implements, including shovels, rakes, trowels, and so forth, use conventional, straight handles because they are easily manufactured. Straight handles are not energy efficient, however, because the user must grip the handle to prevent it from sliding in the user's hands. To prevent blisters and fatigue, the user must increase the grip pressure on the handle, resulting in greater stress on the muscles, tendons, joints and limbs. Various types of angled handles have been developed in an attempt to overcome these drawbacks. Angled handles try to take advantage of a user's body shape and position the arm, wrist, hand and torso in a more relaxed posture.
As one example of many, U.S. Pat. No. 5,771,535 discloses a utility handle for use with a plurality of implements. The handle includes a shaft portion and a handle portion, the handle portion including a plurality of grip portions. The grip portions are positioned such that the user may grasp the handle in a variety of comfortable and ergonomic positions to relieve stress and fatigue occurring during use. In general, the handle includes two portions; an elongated shaft portion and a handle portion. The handle portion includes at least one handhold or grip portion positioned perpendicular or at a slight angle to a longitudinal axis or centerline of the shaft portion. In the preferred embodiment, the handle section includes three grip portions. Two of the grip portions extend perpendicular to the longitudinal axis of the shaft portion. The third grip portion extends outward at an angle from the longitudinal axis of the shaft portion. The third grip portion allows the user to position one hand at an angle to the longitudinal axis of the shaft portion while the other hand is positioned perpendicular to the longitudinal axis of the shaft portion. Grasping the handle in this position; i.e., placing the user's hands where indicated, enables the user to transmit increased energy to the implement while minimizing nonproductive or wasted energy in the form of friction or gripping force.
In terms of shorter, single-handed tools, U.S. Pat. No. 4,950,013 teaches a trowel which is easily inserted into the ground, and is easily rotatable by virtue of an offset handle and an asymmetric blade structure. This purportedly permits easy loosening of earth around plants and the like through the utilization of a handle which is substantially offset from the center line of the trowel to simultaneously provide a pushing post and a lever arm such that the heel of the palm is utilized to press the point of the trowel into the earth. This same offset handle is utilized along with an asymmetric trowel blade to permit easy rotation of the blade, such that upon insertion, the trowel may be rotated by the side or heel of the hand due to the lever arm provided by the offset handle, so as to easily rotate the blade even after insertion of the blade into packed, hardened earth.
U.S. Pat. No. 5,606,772 is directed to a handgrip device for use with tools and utensils. The primary handgrip has multiple angles by which the hand can grip the shaft of a tool or utensil, thus malting the grip ergonomically efficient. When used in combination with a secondary cross-handle, a tool or utensil can become quite easy to use and comfortable to operate. The primary handgrip device of this invention has a grip that slides over, or is made integral with, the end of the shaft of a tool or utensil. The handgrip has a multiply-angled surface, in which the primary hand can assume a substantially straight-angled position (180 degree angle) with respect to the axis of the wrist. The correct hand position varies with each tool and with each work surface. The proper grip angle for a particular task allows the hand to maintain a straight angle with respect to the wrist axis, while also imparting the driving force of the arm into the shaft of the tool.
U.S. Pat. No. 6,662,406 resides in a garden tool including a work-engaging head joined by a shank to a plastic handle. The handle has a relatively rigid plastic core body. A cavity is formed in the handle to divide it into forward and rearward portions. The cavity is filled with a flexible and resilient material to accommodate flexing of the rearward portion relative to the forward portion. A flexible and resilient gripping sheath covers the outer surface of the core body except for the cavity. In one embodiment the cavity is in the core body and includes a notch. For digging tools, such as trowels, the notch is formed on the lower side of the core body adjacent to the distal end, while for pulling or raking tools, such as plows, the notch is formed on the upper side of the core body adjacent to the working end. A recess may be formed in the core body opposite the notch for cooperation with the notch to define a narrow hinge. In another embodiment the cavity includes an aperture extending laterally through a lobe extension of the grip sheath, and in yet in another embodiment the cavity includes notches formed on upper and lower sides of the core body and defined by a hinge interconnecting the forward and rearward portions of the handle.
Practically every hand tool has a natural arc of attack and motion associated with it. Typically there is a primary line of attack within a plane and a larger range of motion within that plane, with end points. The end points may describe an 80 to 100 degree arc for a short handled garden tool, Longer handled tools may have a broader natural arc of attack.